It has been suggested that genetic factors may contribute to alcohol and nicotine co-dependence (AD+ND). Glutamatergic pathway plays important functional roles in addiction. Glutamatergic pathway genes have been demonstrated to be associated with smoking related traits and human variation in alcohol response by genome-wide studies. However, the genetic functional variants underlying AD+ND are largely unidentified. This study mainly aims to identify the potential functional variants underlying AD+ND in glutamatergic pathway, in particular, the variants with low frequencies or weak effects. We select five target genes, including GRIN2B (glutamate receptor, ionotropic, N-methyl D-aspartate 2B), GRM1 (glutamate receptor, metabotropic 1), GRIK1 (glutamate receptor, ionotropic, kainate 1), GLRA2 (glycine receptor, alpha 2) and NTRK2 (neurotrophic tyrosine kinase, receptor, type 2). These regions will be sequenced in a relatively large size of sample (448 AD+ND cases and 448 controls) by a novel next generation sequence approach, i.e., targeted paired-end multiplexed (TPM) sequencing. Both individual effects and joint effects of the five genes on AD+ND will be tested in two independent samples. If successful, this study would make big progress in the research on the mechanism of AD+ND and may be helpful in developing novel and effective treatment and prevention strategies for AD+ND. Furthermore, the expected findings could provide a much detailed map of genetic variants, in particular, rare variants, in the five target regions, which would lay a foundation for future investigation on genotype-phenotype relationship. PUBLIC HEALTH RELEVANCE: This proposed project will search for causal loci for alcohol and nicotine co-dependence, which will help us better understand the biological basis of this phenotype. The expected findings would significantly contribute to the improvement of public health.